In certain mechanical or structural applications it is necessary to effectively prevent the possibility of a spark being generated between two conductive fixing elements, or between a fixing element and another conductive element, which are at a different electric potential. These different electric potentials can be caused by the presence of an electric current, by electric impacts such as lightning or an atmospheric discharge, by a static charge due to friction, etc.
In some applications, preventing these discharges can be a safety requirement, such as for example in the fixings in border areas or of areas inside the fuel storage tanks of aircraft.
There are several known devices for preventing these discharges from occurring between fixing elements, one of which consists of covering the conductive fixing elements with a device in turn comprising a cap and a washer, both made of non-conductive material.
These devices require at least including an additional washer providing a thread in which the corresponding cap will be fixed. This washer increases the thickness that the fixing elements will have to cover (they will then have to have extra length), which affects the way in which the charges are distributed, while at the same time it provides a limited increase in weight, both because of the presence of the washer and because of the necessary extra length of the fixing element. If these devices are used in small amounts, the extra weight will have an insignificant impact, but when these devices are used widely in a structure, the impact of the weight will then be considerable, which is not desirable in certain applications such as in aircraft for example. For that reason, in these applications in which the impact of the weight is highly undesirable, it is necessary to keep the number of components at a minimum and those components must be as small as possible as regards standard protective elements.
The present invention is aimed at solving these drawbacks.